Update helpers.py (#84)

* Update helpers.py

May be fail to minimize,the minimize will return res.fun with a array(0.0), and get res.fun will get an Exception

* Update helpers.py


Thanks to fmfn's advice:
Can you change to if not res.success:? This is more pythonic.

Author: zhangchuangnankai

bayes_opt/helpers.py

@@ -59,6 +59,10 @@ def acq_max(ac, gp, y_max, bounds, random_state, n_warmup=100000, n_iter=250):
                        bounds=bounds,
                        method="L-BFGS-B")
 
+        # See if success
+        if not res.success:
+            continue
+           
         # Store it if better than previous minimum(maximum).
         if max_acq is None or -res.fun[0] >= max_acq:
             x_max = res.x